An 11-year-old girl was sexually assaulted in Napier yesterday afternoon.

Police are looking for a slim caucasian man in his early 20s, who is believed to be responsible for the attack, which happened near the red Chinese bridge on the Georges Dr green belt.

The clean-shaven man had short, straight brown hair and brown eyes. He was wearing a long-sleeved blue checkered shirt, black jeans and a yellow plastic watch on his right wrist.

Constable Steve Leonard said it was a relatively busy time of day, with passing traffic and people on foot.

''This green belt area near the red bridge is a popular shortcut, especially for school students, so we are hoping someone will have seen the incident or hopefully be able to identify the person we are looking for,'' Mr Leonard said.

Anyone with information about the incident should contact Napier police on 06 831 0700 or information can be left anonymously on Crimestoppers 0800 555 111.